I'll throw a couple of options out to you although they aren't Stag so take it FWIW.
AMEETEC ARMS has complete M4 lowers w/ 6-pos stock for
$200 here.They also have complete lowers w/ A1 stocks for
$200 here.AMEETEC is out of stripped lowers (or at least they aren't listed on their site anymore). An option I've seen is
Essential Arms here for $77.
I have no experience with Essential Arms and have limited experience with AMEETEC as I only have one of their complete M4 lowers w/ 6-pos stock. It is very nice however and the finish is as good as my Bushy and slightly better than my 6920's (There are two small specks of missing finish where it appears a tiny piece or two of foreign matter were present when the finish was applied.)
Again, FWIW, and I wish you luck,
Scott